The state of the art includes continuous casting machines for steel strip, or similar products, wherein the crystallizer consists substantially of two rollers, which are arranged between lateral containing walls and rotate in opposite directions to convey the liquid steel downwards and thus form the cast product.
In such continuous casting machines, one of the main problems is the need to form, in the substantially V-shaped compartment which is created between the two rollers, a meniscus of liquid steel which is possibly uniform and homogeneous.
In the state of the art, the meniscus is usually formed with the help of a discharge device directly connected to the lower part of the tundish and provided with a lower end arranged either in proximity of the upper level of the meniscus or just below, that is to say, inside the meniscus.
In such conventional devices, there is no guarantee that the meniscus will be homogeneous and uniform, since the liquid steel is discharged directly into the bath which forms the meniscus, with the kinetic energy appropriate to the different level of the tundish and the crystallizer; the result is turbulence which has a negative affect especially in the zones of the meniscus wherein the contact occurs between the liquid steel and the rollers and/or the lateral containing plates.
U.S. Pat. No. 6,095,233 discloses a device to feed the steel between the rollers consisting essentially of a SEN (Submerged Entry Nozzle) shaped like an elongated trough and provided with holes or slits able to direct the flow of steel against the rollers, just under the meniscus. Between the upper tundish and the SEN there is a discharge element, whose section changes from circular to elongated, before it is inserted into the SEN. The main disadvantage of this known device is that the steel is fed onto the meniscus discontinuously, by means of the eyelets which are made on the lateral wall of the SEN. Consequently the feed of the liquid steel in the meniscus along the generatrix of the roller is not uniform.
U.S. Pat. No. 3,867,978 discloses a device to introduce steel into a mold for continuous casting, wherein the steel is discharged into a crystallizer by means of a SEN consisting of a submerged tube which ends in a plate elongated in the direction of the vertical casting axis. The plate on the one hand prevents the hot jet from hitting the solidifying skin and thus re-melting it, and on the other hand it feeds the meniscus. The SEN described in this known device, which does not use a roller-type crystallizer, is not able to feed the liquid steel along the meniscus in a uniform manner.
JP-A-02055643 discloses a device for the continuous casting of metal strip by means of a roller-type crystallizer, wherein a SEN is provided composed of a trough with inner walls substantially converging downwards and parallel to the lateral walls, and wherein on the lower part of the inner walls there are horizontal holes which allow the cast steel to pass into the lateral compartments of the SEN, between the inner walls and the lateral walls, to then be directed towards the meniscus above. This device has the following disadvantages: when there are high quantity flows of liquid steel it increases the turbulence thereof, because all the steel goes directly on the meniscus; it is not able to make the temperature of the liquid steel uniform in the liquid pool of the crystallizer, between the two rollers; it can create, under the SEN, a dead zone where the liquid steel stagnates and where inclusions can collect, which compromise the quality of the cast strip.
Applicant has devised and embodied this invention to overcome these shortcomings of the state of the art.